The overall objective of the proposed research is to understand the neural systems underlying the expression of emotion in primates. We have focused on elucidating mechanisms underlying the expression of fear and anxiety. This is an area of great importance because when appropriate, fear- motivation behaviors are adaptive; however, when overly intense of expressed out of context, extreme fear is characteristics of many forms of psychopathology. Studies will focus on the role of the amygdala in mediating fearful states. Although many studies have been performed in rodents, studies in nonhuman primates are important because they provide a basis for understanding the role of the amygdala in humans. Important differences in social behavior and cortical amygdala linkages between rodents and primates highlight the necessity of performing research to close the psychopathology are found in nonhuman primates. We will use state-of-the-art techniques to lesion the amygdala and its nuclei. Most prior studies in primates have used lesioning techniques that have not been selective, resulting in damage to other sub-cortical and cortical regions. In addition to complete amygdala lesions, lesions of the central and lateral nuclei will be made. These sites are of interest because they are the major points at which information enters and leaves the amygdala. The effects of these lesions on the following parameters will be assessed: 1) classically conditioned autonomic responses, 2) ethologically relevant threatening stimuli, and 3) affiliative and defensive behavior expressed in social situations. Eventually, these studies will define biological mechanisms regulating the expression of the primate's adaptive responding to threatening stimuli. These findings will provide insight into mechanisms mediating maladaptive responding in humans, which is characteristic of fear-related psychopathology.